Call CheckLinearizedFirstPage() when loading the first linearized page.
Call CheckLinearizedFirstPage() when loading the first linearized page.

Otherwise CheckLinearizedFirstPage() has no other callers.

BUG=pdfium:330
R=jun_fang@foxitsoftware.com

Review URL: https://codereview.chromium.org/1543193002 .

andoma/pdfium,DrAlexx/pdfium,DrAlexx/pdfium,andoma/pdfium,andoma/pdfium,andoma/pdfium,DrAlexx/pdfium,DrAlexx/pdfium